Nonlinear Behavior in the Optical Spectra of Solid Fullerene C60
ABSTRACT Optical emission spectra of solid C60 have been recorded at 1.9 K. Several vibronic transitions are observed. In particular the dependence of the emission spectrum with respect to the excitation intensity has been studied at room temperature and at 12 K under excitation with 514.5 nm and 488.0 nm laser radiation. The emission intensity increases with excitation intensity stronger than linear. At higher excitation powers an additional optical transition centered at 16500 cm−1 becomes dominant. In an absorption experiment in solution (1.4-10−5 mol/l), the absorbed power of light is also nonlinear with respect to the excitation power.